The present invention relates to a method of improving radial run out (RRO) of a wheel rim, more particularly to a method of reducing an n-order component of RRO.
The radial force variation (RFV) of a vehicle wheel, namely, an assembly of a rim and a pneumatic tire is one of factors to be considered when decreasing vibrations of a vehicle during running especially high-speed running.
In order to reduce vehicle vibrations, in the laid-open Japanese paten application JP-A-8-66957, the tire tread is buffed to reduce the radial run out (RRO) and thereby to reduce RFV. In the laid-open Japanese paten application JP-A-7-156293, in order to reduce RRO, a balance weight is applied to the inner surface of a pneumatic tire.
These measures are for the tires. But the wheel rims also have RRO of which value usually ranges from about 0.1 mm to about 0.3 mm. when the wheel rim has a relatively large RRO, even if the RFV of a tire and rim assembly is reduced by adjusting the tire as above under particular running conditions (e.g. speed range), there is a possibility of increasing in the RFV under different conditions.
It is therefore, an object of the present invention to provide a method of improving RRO of a wheel rim, by which the RRO and RFV of an assembly of the wheel rim and a pneumatic tire can be effectively improved.
According to one aspect of the present invention, a method of improving radial run out (RRO) of a wheel rim having a pair of bead seats for tire beads, comprising
measuring a radial run out Y1 of one of the bead seats around the wheel rim,
measuring a radial run out Y2 of the other bead seat around the wheel rim,
finding an average Y of the radial run out Y1 and radial run out Y2 around the wheel rim,
analyzing the average Y around the wheel rim to find out an n-order component which is largest in the peak-to-peak amplitude,
obtaining the peak-to-peak amplitude of the n-order component as RRO value X,
finding minimum position(s) at which the n-order component becomes minimum and determining deep position(s) P on the wheel rim corresponding to the minimum position(s),
determining the length L of a corrective tape as a value within a range of from 0.8 to 1.02 times a length L0,
applying a corrective tape to one of or alternatively each of the bead seats at each said deep position P, wherein
the corrective tape is made of a synthetic resin and has a thickness t of from 0.1 to 0.5 mm, and
said length L0 is defined by the following precision expression (1) or alternatively simplified expression (2)                     L0        =                              R                          π              xc3x97              n                                xc3x97                      arcsin            ⁡                          (                              X                                  t                  xc3x97                  a                  xc3x97                  1.3                                            )                                                          (        1        )                                L0        =                                                            100                xc3x97                R                xc3x97                X                                            360                xc3x97                t                xc3x97                a                xc3x97                n                                      ⁢                          xe2x80x83                        ⁢            where            ⁢                          xe2x80x83                        ⁢            0                     less than                       L0            R                     less than           0.28                                    (        2        )            
wherein
L0 is a value in mm,
X is a value in mm,
n is a positive integer of the order number of the n-order component,
t is a value in mm,
a is a multiplier which is 0.5 when the corrective tape is applied to one of the bead seats or 1.0 when the corrective tape is applied to both of the bead seats,
R is the circumference in mm of the bead seat,
pi is the circle ratio (=3.14159 - - - ), and
the unit of the argument of arcsine is radian.